The present invention relates generally to a bevel gear differential mechanism for transmitting rotary power between input pinions and side gears, which are connected to driven vehicle wheels. More particularly, it pertains to reducing driveline clunk due to axle lash.
In a conventional differential mechanism, a pair of side gears and a pair of pinions are installed in a differential casing such that gear teeth on the side gears mesh with gear teeth on the pinions. It is conventional to use a shim selected with a predetermined fit to space the side gears axially away from the inner surface of the casing and axially closer to the pinion gears.
When the operator of a motor vehicle having such a differential tips-in, i.e. rapidly depresses the accelerator pedal from a coasting or braking condition, driveline clunk, a dull objectionable sound is produced, partially due to a condition called rear axle lash. The shim that is used to locate the side gear relative to the pinions often does not position the side gear correctly and permits excessive axial clearance between the side gears and the differential casing. When torque transmitted through the differential is applied abruptly or its directional sense is reversed abruptly, this clearance is closed by an axial thrust force between the adjacent teeth, thereby causing the side gears to impact the casing at relatively high speed and producing the characteristic driveline clunk. Driveline clunk can also occur in a driveline upon shifting an automatic transmission from Park to Drive or Reverse, from Reverse to Drive, and from Drive to Reverse.
There is a need to avoid driveline clunk by correctly, reliably locating the side gears relative to the pinions in the differential casing such that rear axle lash is avoided. Preferably a resilient force can be produced that continually urges the side gears toward the pinions and prevents their impacting the inner surfaces of the casing. In addition, that force should provide damping that would attenuate driveline torque transients.